Make GUI Button Open Another GUI

What I need is to have the same GUI stay, but when the person goes to the menu and selects Editors > NPCSpawner, I need it to change from the default interface that's there (NPCSpawner interface) to the Other GUI (yes, it's called "Other"):

You have cross-posted your last two questions here, and I will hold off helping til I know if you've cross-posted this one as well. Most of us as volunteers don't want to waste our time answering questions that have already been answered elsewhere.

Edit, yeah you have cross-posted here daniweb.com and lord knows where else, and you didn't warn us. Please read this link to see why it bothers us: BeForthrightWhenCrossPostingToOtherSites. You know our time is valuable too, but you don't seem to care. Good luck getting help.

The proper thing to do is to notify us of all cross-posts with links. Again, please see the link I've given you to see why this is important. You still can do this you know, and if you want to avoid being labeled as someone folks will avoid helping, I suggest that you do this.